JP4207788B2 - Injector nozzle hole machining method - Google Patents

Description

  The present invention relates to an apparatus and a processing method for processing a plurality of micro holes in an injector nozzle, and more particularly to micro hole processing of an injector nozzle that can obtain a smooth molten surface with little variation in hole diameter.

  2. Description of the Related Art In recent years, direct injection gasoline engines or diesel engines have become more active in reducing fuel consumption, purifying exhaust gas, and increasing output. In general, in a fuel injection valve or the like of an internal combustion engine or the like, it is necessary to reliably shut off the fuel or flow an appropriate amount of flow by opening and closing the valve. The injector nozzle is mounted at the tip of the nozzle holder, and high-pressure fuel enters the peripheral portion of the nozzle and pushes up the needle valve to inject fuel. Since this injector nozzle is used under severe conditions of high temperature and high pressure, it is finished with precision processing using a special material, and its inner surface shape is a fuel spray suitable for the combustion chamber shape High finish surface is required.

  On the other hand, since the performance of a gasoline engine is governed by the injection characteristics of the gasoline to be injected, its uniformity has recently become important, with a single hole having a diameter of 40 to 100 μm (mainly about 80 μm) or Strict levels are required for the finished state of drilling in the perforations.

  Conventionally, drilling has been the mainstream for drilling to provide a cylindrical single hole or perforation at the tip of the injector nozzle. By removing the burr at the inlet / outlet generated by drilling with a laser beam, the diameter of the injector nozzle hole Variation can be suppressed, and the injection amount can be stabilized and spray variation can be suppressed.

  As other processing methods, high energy processing methods such as laser light and electric discharge processing are employed in part. However, in order to obtain uniform cylindrical fine holes by these methods, the tip of the base material must be round, and adhesion of the melt on the exit side is inevitable, and the enlargement of the holes due to the characteristics of the laser There was a problem in terms of accuracy.

  In order to solve such a problem, Patent Document 1 shown below relates to a method for preventing the expansion of molten holes generated on the heat input side by the laser beam, a method for imparting a temperature gradient to the inner and outer surfaces, or an inorganic material on the surface. A laser drilling method by a method of disposing a film is disclosed. However, these methods also increase the number of processing steps, such as a heater for heating or an inorganic coating on the surface. There is also a technique for preventing reattachment to the inner surface of a processing hole by sucking gas generated by melting or oxidized dust.

  As described above, there is a demand for a laser drilling technique for preventing deposits and improving uniformity by discharging and removing a melt and preventing an increase in melt diameter on the surface side.

JP 2000-202666 A

  The above technique aims to improve the cylindrical accuracy of the fine holes of the injector nozzle, and there is no problem with flat drilling that allows easy discharge and removal of the melt. In drilling a workpiece, there are problems that the hole diameter becomes small and the hole diameter varies.

  In view of the above-mentioned problems, one of the objects of the present invention is to supply a combustion gas together with a laser beam for drilling, and to promote the progress inside the melted portion by this gas flow to smooth the melted portion. The present invention relates to a drilling apparatus and a processing method.

In order to satisfy the above object, an injector nozzle hole machining method according to the present invention supplies a machining assist gas to a laser light irradiation region of an injector body with a negative pressure in a nozzle conduit provided inside the injector body. Injector nozzle drilling method that uses a laser drilling machine to process a nozzle hole communicating with the nozzle guide by irradiating a laser beam to the injector body, and obtaining an operation signal of the laser drilling machine, By controlling the negative pressure applied to the inside of the body , an arbitrary negative pressure within a predetermined negative pressure range is generated in the fine hole opened at the laser light irradiation point, and the flow of processing assist gas heated to a high temperature by the laser light Is controlled , and the melted surface is smoothed by continuously sucking out from the melted portion of the open tip to the nozzle guide.

  Furthermore, in the injector nozzle hole machining method according to the present invention, the predetermined negative pressure range is 200 mmHg (25.8 kPa) or more.

  More preferably, in the injector nozzle hole machining method according to the present invention, the predetermined load range is 250 mmHg (32.2 kPa) or more.

  Even more preferably, in the injector nozzle hole machining method according to the present invention, the predetermined load range is 275 mmHg (35.5 kPa) or more.

  Furthermore, the injector nozzle hole processing method according to the present invention is characterized in that the processing assist gas is supplied to the laser light irradiation region using a gas supply nozzle and irradiated with the laser light through the supply hole of the gas supply nozzle.

  Furthermore, in the injector nozzle hole machining method according to the present invention, in order to maintain a predetermined negative pressure, a first suction maintaining step for performing suction while maintaining an arbitrary negative pressure within a predetermined negative pressure range; Thereafter, a second suction maintaining step for preventing the negative pressure in the nozzle passage from fluctuating during laser processing is provided.

  According to the present invention, an injector nozzle having improved fuel injection characteristics that improves the smoothness of the inner wall due to repetition of melting and solidification occurring in a short time in units of seconds by laser light, and has a back hole diameter of It can be processed as a cylindrical through-hole with suppressed variation in hole diameter without being reduced, and spatter on the back surface can be removed.

  Hereinafter, embodiments of the present invention (hereinafter referred to as embodiments) will be described with reference to the drawings.

  FIG. 1 is a schematic diagram showing an outline of a fine hole machining apparatus for an injector nozzle according to an embodiment of the present invention. The injector 1 is fixed to an injector fixing jig 6, and a flow path provided in the injector fixing jig 6 is connected to the inside of the injector and the negative pressure gauge 5. The negative pressure gauge 5 is connected to the vacuum pump 3 together with the main regulator 32 and the sub-regulator 33. The negative pressure is primary controlled by the main regulator 32 at 200 mmHg or more (for example, 400 mmHg or less), preferably 270 mmHg or more (for example, 325 mmHg or less), but in this embodiment, in order to control the negative pressure more accurately, The pump controller 4 controls the vacuum pump 3 and the sub-regulator 33 according to the negative pressure value of the negative pressure gauge 5. Further, the pump controller 4 obtains an operation signal of the laser drilling machine 20 to reduce pressure fluctuation due to an increase in assist gas inflow when the injector nozzle hole 30 is drilled. With this configuration, it is possible to control at more preferable 275 mmHg or more (for example, 325 mmHg or less).

FIG. 2 is an enlarged view of a laser irradiation unit in the fine hole machining apparatus for an injector nozzle according to the embodiment of the present invention. Using such an apparatus, the inside of the nozzle passage is sucked with a negative pressure of 300 mmHg or less during the micro-hole processing of the injector by laser light irradiation. The assist gas uses a mixed gas of argon (Ar) and about 5 percent oxygen (O ₂ ), but the same effect can be obtained with Ar alone, O ₂ alone, or N ₂ alone. Furthermore, the assist gas is pressurized to 0.2 MPa.

  The purpose of the assist gas is to prevent oxidation of the molten metal and to prevent excessive melting, and to reduce the temperature unevenness caused by laser drilling. Further, the adhesion of the melt is prevented by the assist gas, and at the same time, the combustion gas and the oxidized dust generated by the melting are sucked to prevent the adhesion to the inner surface of the processing hole. That is, the removal of unnecessary melt is promoted by sucking the assist gas and the combustion gas at high speed.

  The specifications and processing conditions of the injector nozzle processed in this embodiment are as follows. Specifically, the injector nozzle material is SUS or SCM (nickel chromium molybdenum steel), the nozzle diameter is D = φ8 mm, t (thickness) = 1.2 mm, and the number of fine nozzle holes is 6-30 holes, 50-150 μm. This is a multi-hole nozzle.

  FIG. 3 is a schematic diagram showing an overview of a laser drilling machine according to an embodiment of the present invention. A YAG-SHG laser is used as the laser, the laser output is 20 w class, and the laser beam diameter is φ20 μm. In response to a command from the control panel 16, the power supply 15 is activated and an activation signal is sent to the pump controller. Next, it oscillates continuously, preferably as a pulse, and is adjusted as laser light suitable for irradiation by the diaphragm 13 and the output mirror 12. The laser light is turned back from the laser oscillator 18 and the shutter 14 is opened, so that it is sent to the reflection mirror 9 and bent 90 degrees. An observation microscope 10 is provided above the reflection mirror 9 via a filter 11 to monitor a processing portion. On the other hand, the processing laser light passes through the condenser lens 8 and has a small diameter and high energy, and is irradiated onto the injector 1.

  Further, in the laser irradiation, the irradiation part is melted by irradiating in a pulse form with a short cycle, and the surface of the melting part is evaporated to remove a minute amount of the skin part. By repeating this process, holes can be formed.

  (A), (b), and (c) of FIG. 4 are schematic views of the fine holes showing the injector nozzle fine hole making process according to the embodiment of the present invention. The laser beam is irradiated for about 10 seconds to make a hole in the injector nozzle.

(A) shows the state which started laser drilling. The laser beam and the assist gas start melting from the laser beam irradiation part to generate a high-temperature melt ₂ and react with O _{2 of} the assist gas, and the laser beam irradiation part becomes hot and the surface evaporates in the laser beam direction. Minute removal and melting are repeated. At this time, the inside of the injector 1 is sucked and has a negative pressure. However, since the negative pressure at this time does not affect the machining, if there is a negative pressure means capable of rapid pressure reduction, the inside of the injector need not be made negative in this step.

  (B) shows a state in which melting has progressed from the inlet side to the outlet side by laser drilling. When the melting proceeds to the outlet side, the melt 2 blows off toward the inside of the injector 1 due to the negative pressure due to suction, and the melting on the outlet side further proceeds together with the high-temperature assist gas. In this way, the spatter on the back surface of the injector can be removed. In the present embodiment, the negative pressure is set to (a) in order to accurately control the negative pressure.

  (C) shows a state in which laser drilling has further progressed. The assist gas heated to a high temperature by the laser beam is further accelerated by suction from the inside of the injector 1. The molten part 2 is blown off by the high-temperature and high-speed assist gas, and the molten surface is smoothed into a cylindrical shape. The melt 2 does not adhere to the inside of the injector 1 by suction and is discharged to the outside of the injector 1 by the vacuum pump 3. Of course, there is a filter in the front stage of the negative pressure gauge 5, and it goes without saying that the oxide dust that the melt 2 has cooled and solidified is recovered.

  FIG. 5 is a schematic diagram showing the relationship between the negative pressure inside the injector, the hole diameter, and the variation (standard deviation) in the hole diameter according to the embodiment of the present invention. The horizontal axis represents negative pressure, the left vertical axis represents standard deviation indicating variation in hole diameter, and the right axis represents hole diameter. The irradiation time of the laser beam is 10 seconds, and the hole diameter is measured by measuring the vertical and horizontal diameters of the holes with the microscope 10 and averaging them to obtain the hole diameter of one hole. Further, the negative pressure was gradually reduced from atmospheric pressure to about 500 mmHg, and each of the 10 pore diameters and the dispersion of the pore diameters at the same negative pressure was determined by standard deviation.

  According to the measurement, the pore diameter was 48 μm at atmospheric pressure and the standard deviation was 3.5. However, as the pressure was lowered, the pore diameter increased, and the standard deviation of the pore diameter decreased with decreasing pressure, and the pore diameter was 57 μm at about 300 mmHg. The standard deviation is 1.7. When the decrease of the standard deviation stops and increases to 400 mmHg, the standard deviation increases to 2, and further increases to 2.2 at 500 mmHg. From this, if the negative pressure is at least 100 mmHg centering on 300 mmHg, a hole diameter with little variation can be obtained, and the hole diameter is 55 μm. Furthermore, if the negative pressure is controlled and within about 300 mmHg and within 25 mmHg, the standard deviation is 1.7.

  Thus, the negative pressure improves the gas flow and suppresses variation in the hole diameter. Therefore, even if the negative pressure increases (becomes 500 mmHg), the variation does not increase basically. The reason why the variation increased from 300 mmHg to 500 mmHg is considered to be caused by the abnormal value because the n number is as small as 10. From the mechanism, the effect is expected to be saturated from 300 mmHg, and the negative pressure does not need to be increased further.

  From the above results, the present embodiment has an effect that the inside of the injector 1 is decompressed, and the hole diameter variation is reduced and a smooth molten surface can be obtained by a high-temperature, high-speed assist gas. In the present embodiment, the injector nozzle drilling method using reduced pressure is used, but there is also a method in which a negative pressure is locally applied to the flat plate from the back side. As another method, it goes without saying that there is a method of further pressurizing the assist gas to make a hole in the injector nozzle.

It is an outline figure showing an outline of a fine hole processing device of an injector nozzle concerning an embodiment of the present invention. It is an enlarged view of the laser irradiation part in the fine hole processing apparatus of the injector nozzle which concerns on embodiment of this invention. It is a schematic diagram showing an outline of a laser drilling machine according to an embodiment of the present invention. It is an enlarged view of the fine hole which shows the injector nozzle fine hole drilling process which concerns on embodiment of this invention. It is a schematic diagram which shows the relationship between the negative pressure inside the injector which concerns on embodiment of this invention, a hole diameter, and the dispersion | variation (standard deviation) of a hole diameter.

Explanation of symbols

  1 injector, 2 melt, 3 vacuum pump, 4 pump controller, 5 negative pressure gauge, 6 injector fixing jig, 7 assist gas nozzle, 8 condenser lens, 9 reflecting mirror, 10 microscope, 11 filter, 12 output mirror, 14 shutter, 15 power supply, 16 control panel, 18 laser oscillator, 20 laser drilling machine, 30 injector nozzle hole, 31 exhaust port, 32 main regulator, 33 sub-regulator.

Claims (6)

The nozzle conduit provided inside the injector body is set to a negative pressure, processing assist gas is supplied to the laser light irradiation area of the injector body, and the nozzle hole communicating with the nozzle conduit by irradiating the injector body with laser light is laser In the injector nozzle hole machining method for machining using a hole drilling machine ,
By acquiring the operation signal of the laser drilling machine and controlling the negative pressure applied to the inside of the injector body , an arbitrary negative pressure within a predetermined negative pressure range is generated in the fine hole opened at the irradiation point of the laser beam. Injector nozzle hole characterized by smoothing the melt surface by controlling the flow of processing assist gas heated to high temperature with laser light and sucking continuously from the melted part of the open tip to the nozzle guide Processing method. The injector nozzle hole machining method according to claim 1,
The injector nozzle hole machining method, wherein the predetermined negative pressure range is 200 mmHg (25.8 kPa) or more. The injector nozzle hole machining method according to claim 2,
The injector nozzle hole machining method, wherein the predetermined load range is 250 mmHg (32.2 kPa) or more. In the injector nozzle hole machining method according to claim 3,
The injector nozzle hole machining method, wherein the predetermined load range is 275 mmHg (35.5 kPa) or more. The injector nozzle hole machining method according to claim 1,
A processing nozzle gas is supplied to a laser beam irradiation region using a gas supply nozzle, and the laser beam is irradiated through a supply hole of the gas supply nozzle. In the injector nozzle hole machining method according to any one of claims 1 to 5,
A first suction maintaining step for maintaining and sucking at an arbitrary negative pressure within a predetermined negative pressure range in order to maintain the predetermined negative pressure;
After the penetration, a second suction maintaining step for preventing the negative pressure in the nozzle passage from fluctuating during laser processing;
An injector nozzle hole machining method comprising:

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